Apple is at its best when it takes an existing idea and turns it into something unique. The new tetraprism “zoom” lens in the iPhone 15 Pro Max is one of the nicest surprises in years.

The tetraprism is a periscope lens, except it's made by folding a prism into waves instead of rotating a long tube of lenses to lie along the length of the iPhone's body. It's such a clever idea, and it's going to make the iPhone's camera system even more flexible.

"At 120mm and an aperture of 2.8, this is a serious portrait lens and creates real background blur, rather than artificial software blur, which can look unnatural," travel photographer Tom Bourdon told Lifewire via email. "I can imagine many photographers will upgrade to this mobile phone simply because of this lens."

The iPhone has been awash with periscope lens rumors for years, but now that it’s here, it’s even more interesting than expected. Before we get into how it works, let’s look at why it’s needed.